Unless otherwise indicated herein, the description in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
In general, a typical image forming apparatus using a electrophotographic method includes a light scanning device that irradiates a surface of a photoreceptor drum with a light beam corresponding to image data, and causes the light beam to scan in a main-scanning direction.
The light scanning device includes a light source, a polygon mirror, an imaging lens, and a reflecting mirror. The polygon mirror reflects the light beam emitted from the light source to cause the light beam to deflectively scan. The imaging lens causes the light beam reflected by the polygon mirror to form an image on a scanned surface. The reflecting mirror reflects the light beam that has passed through the imaging lens toward the scanned surface.
In this type of light scanning device, a rotational vibration of a polygon mirror sometimes transmits to an optical element such as an imaging lens or a reflecting mirror to vibrate the optical element. Vibrating the optical element causes a light beam on a scanned surface to generate a positional deviation in a sub-scanning direction and then causes an image failure such as a print-density unevenness or jitter.